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Furniture manufacturer discovers the benefits of polypropylene

Local corporate furniture manufacturer Dauphin HumanDesign Group (Dauphin) reports that it is investigat- ing using polypropylene more extensively in its office furniture designs, necessitating further research and development (R&D).

The company believes that using polypropylene to replace traditional materials in its furniture designs holds the potential to reduce manufacturing costs, as well as to reduce the carbon footprint of its products.

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Dauphin R&D consultant Ian Boyd says that the company stumbled on the idea of investigating polypropylene to replace a number of components when it was seeking ways to reduce the frequency of production variables in its manufacturing process.

A problem arose with the significant varia- bles encountered in manufacturing tolerances by local component manufacturers, resulting in difficulty maintaining reliable product output. Boyd explains that this was experienced first-hand with one of the company’s chairs that had nylon armrests.

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“Nylon is a rigid material, and the slightest anomalies to the specified dimensions resulted in either the armrest not fitting onto the metal frame, or fitting too loosely,” he says.

Investigations into the problem led the company to experiment with polypropylene as a substitute for nylon, owing to it being a more versatile material, as well as being manu- factured locally. With minor improvements made to the design, the company managed to shave 66,67% off the manufacturing cost of the armrest component, prompting further investigations into where polypropylene can be successfully applied.

Boyd believes that the use of polypropylene enables the company to achieve better lead times for new orders, and adds that it is more cost effective as it is locally manufactured and negates the need to import more-expensive materials. It also results in a reduced carbon footprint for the company and its products.

“Polypropylene products potentially enable us to remain competitive when the inter- national market is not balanced. Corporate clients are environmentally conscious, but it seems that when they import products from China, the green consciousness does not count anymore,” Boyd argues.

He adds that, in solving the armrest problem, the company invested in new polypropylene injection-moulding tooling, which, fortunately for the manufacturing department, amortised quickly, owing to a significant initial contract.

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Dauphin reports that research is currently being undertaken to establish where polypropylene can be successfully substituted in other parts of its office furniture range. “We believe we are moving the boundaries in injection-moulded furniture by undertaking local R&D activities,” he notes.

Boyd points out that existing furniture models need to be redesigned to some extent, owing to polypropylene having different compression and tension characteristics than the traditional materials, such as nylon and aluminium.

In undertaking his research, Boyd uses finite element analysis on the existing designs to better understand how and why the designs look the way they do, what materials were used and where weak points in the old designs and bottlenecks in the existing production line are to be found.

Further, Boyd extensively uses three- dimensional modelling and wooden mock-up models to gain a better understanding of how the prototype designs will behave under stress.

Dauphin also liaises with its German parent company to see where, within the company, the components can be manufactured most cost effectively. The company manufactures or sources components from Germany, South Africa, Taiwan and Switzerland.

However, substituting polypropylene derivatives poses two challenges, namely increasing the strength of current designs, owing to the need to compensate for the lack of material strength, and getting the new material into production as quickly as possible with the fewest problems.

Another challenge is to find a balance between aesthetically pleasing forms, which, in the case of polypropylene, are dictated by function.

Boyd uses test rigs to test individual components of furniture designs on a trial-and-error basis. He adds additional ribs to designs to increase rigidity and prevent warping. “We are experimenting with different injection rates, mould temperatures and cooling techniques, until we find the most suitable solution,” he says.

He concedes that the R&D work is, at this stage, an ambitious undertaking to find the ideal method to equalise the compression and tension properties of polypropylene.

He notes that the plastic products are tested to withstand significant forces that the products are unlikely to encounter during normal use. “We are aiming to achieve a 1,7-t breakpoint on a polypropylene chair’s base arms, and are testing our components to achieve standards set by the US Business and Institutional Furniture Manufacturer’s Association.

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He adds that the R&D team is starting to achieve the desired strength in the design, but now have to find the right moulding technique, while still making the design aesthetically pleasing. “The challenge is to find an optimum balance between these elements,” Boyd says.